Hose End Fittings

ABSTRACT

An end fitting for a composite hose of the type comprising a tubular body of flexible material arranged between inner and outer gripping members. The end fitting comprises a first member adapted to be disposed within the hose, and a second member adapted to be disposed around the outside of the hose, whereby the end of the hose can be sealed between the first and second members, and wherein at least part of the end first member and/or at least part of the first member is made of a composite material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a filing under 35 U.S.C. 371 of InternationalApplication No. PCT/GB2008/003121 filed Sep. 15, 2008, entitled“Improvements Relating to Hose End Fittings,” claiming priority of GreatBritain Patent Application Nos. 0718018.5, 0718019.3 and 0718020.1, allfiled Sep. 14, 2007, which applications are incorporated by referenceherein in their entirety.

FIELD OF THE INVENTION

This invention relates to an end fitting for a hose, particularly hosewhich can be used in cryogenic conditions. The invention also relates toa hose incorporating the end fitting.

Typical applications for hose involve the pumping of fluids from a fluidreservoir under pressure. Examples include supplying of domestic heatingoil or LPG to a boiler; transporting produced oilfield liquids and/orgases from a fixed or floating production platform to the cargo hold ofa ship, or from a ship cargo hold to a land-based storage unit;delivering of fuel to racing cars, especially during refuelling informula 1; and conveying corrosive fluids, such as sulphuric acid.

BACKGROUND OF THE INVENTION

It is well known to use hose for the transport of fluids, such asliquefied gases, at low temperature. Such hose is commonly used totransport liquefied gases such as liquefied natural gas (LNG) andliquefied propane gas (LPG).

In order for the hose to be sufficiently flexible, any given length mustbe at least partially constructed of flexible materials, i.e., non-rigidmaterials.

The present invention is directed to composite hose. Conventionalcomposite hoses are made of layers of polymeric films and fabricssandwiched between an inner and outer helical metallic wire. The hose isconstructed by wrapping around a mandrel, in sequence, the inner wire,combinations of films and fabric, and the outer wire. The inner andouter wires have the same helical pitch but are offset by half the pitchlength to form a corrugated hose wall profile. The resulting tubularstructure is then extracted from the mandrel and terminated with endfittings. The end fittings are typically constructed of a metallic tailand a ferrule. The tail has two parallel helical groves machined intothe outer surface which matches the double helix formed by the inner andouter wires. The tail is inserted into the bore of the hose with aferrule on the outside. Depending on the application, the end of thehose pack may be bound, capped with a rubber cuff or impregnated with atwo part epoxy resin, and the ferrule is then crimped or swaged down onto the tail to retain the end of the hose. A hose of this general typeis described in European patent publication no. 0076540A1. The hosedescribed in this specification includes an intermediate layer ofbiaxially oriented polypropylene, which is said to improve the abilityof the hose to resist the fatigue caused by repeated flexing.

In our earlier patent application WO01/96772, we described a newcomposite hose which incorporated a braid with the film and fabriclayers sandwiched between the two helical wires. We also described a newend fitting for this hose. Further improvements to the hose and endfitting were described in our patent applications WO04/044472 andWO04/079248. These composite hoses may be provided with a large bore andare typically aimed at ship to ship fluid transfer operations which aregoverned by the requirements of the International Maritime Organisation(IMO). The IMO requirements for hoses (International Code for theConstruction and Equipment of Ships Carrying Liquefied Gases in Bulk—the“IGC Code”) are demanding (for reasons of safety) that the hose burstpressure must be five times the maximum working pressure at the extremeservice temperature. The maximum working pressure typically ranges fromthe minimum required by IMO of 10 barg up to 20 to 30 barg.

It is important that the end fitting is able to accommodate safely thestresses induced by the IMO burst pressure test. End fittings are madefrom metallic components and the tail in particular must be able toaccommodate the hoop stress induced by the internal pressure which isgiven to first approximation by the Barlow formula which states that thehoop stress is equal to the product of the internal pressure and theinternal diameter divided by twice the wall thickness of the tubeforming the tail. The allowable stress is determined by the standardpressure vessel design codes such the ASME Boiler and Pressure VesselCode as a proportion, two thirds say, of the tail material's yieldstress. Typical tail materials are carbon steels for non cryogenicapplications and austenitic stainless steels for cryogenic service i.e.typically temperatures below 150° K. Carbon steels are not suitable forcryogenic service as they are brittle at very low temperatures.

Exemplary austenitic stainless steel grades for cryogenic service arethe “series 300” which do not exhibit low temperature brittleness. Theimportant material properties are the yield stress (YS), the yieldstrain (EY), the ultimate tensile strength (UTS), the failure strain(EF), the elastic modulus (E), the density (RHO), the thermalconductivity (K) and the thermal expansion coefficient (CTE). Theseproperties vary over the range from ambient (293° K) to cryogenictemperatures (4° K for Liquid Helium or 77° K for Liquid Nitrogen[LN₂]). In general, the strength increases with reducing temperature.This is illustrated by considering as an example AISI grade 304 (8 g/ccdensity) which is a commonly used austenitic stainless steel forcryogenic service. The YS & UTS of 304 at room temperature is about 250MPa & 590 MPa respectively, and at LN₂ temperature (77° K) about 400 MPa& 1525 MPa respectively. While there is some reduction in the ductilitywith EF reducing from 60% at ambient temperature to 40% at LN₂temperature, there is more than adequate ductility with 304 at thiscryogenic temperature. Although this increase in strength is consideredbeneficial, designers of cryogenic pressure vessels tend to rely on theminimum ambient temperature specifications. The ambient LN₂ temperatureelastic moduli for 304 are 193 GPa and 205 GPa respectively.

An important design issue for cryogenic equipment is the effects of thedimensional changes and thermal gradient transients associated with thecirca 215° K temperature change room ambient to cryogenic serviceconditions. Steels such as 304 are thermally conductive and they willcontract with decreasing temperature. The thermal conductivities for 304at room temperature and LN₂ temperature are 8 & 15 W/m.° K respectively.The average CTE over this temperature range is 13×10⁻⁶° K⁻¹ i.e. alength contraction of about 3 mm/m for this temperature difference of216° K.

This contraction presents a problem for conventional end fittings inconditions of thermal shock where the end fitting is rapidly exposed tocryogenic fluid. This may cause a transient differential thermalcontraction in the radial direction between the tail and ferrule,resulting in some leakage. This is further accentuated in long termservice conditions if an epoxy resin is relied on as a filler to sealany small leak paths. The CTE for epoxy resign is about 50×10⁻⁶° K⁻¹ to80×10⁻⁶° K⁻¹ and therefore the resin will try to contract more than theadjacent austenitic stainless steel. With repetitive thermal cycles theresin bond with the steel may fail and a leak path may subsequentlydevelop. This is a known problem in the field which may be addressed bycareful control of the thermal exposure profile and/or the detaileddesign of the end fitting assembly.

With the end fitting described in WO04/079248, because of the advantageof having a separate ring to provide the sealing function, the sealingactivation is carried out to compensate for the thermal shock and wehave found this to be a satisfactory solution in our full scale testingwith both LN₂ and LNG.

We have also found it beneficial to construct the tail of 36% Nickel,balance Iron metal alloy, sometimes called by the Trademarks Invar andPernifer 36, (density 8.1 g/cc), which has comparable strength toaustenitic stainless steels but with a substantially lower CTE. Atambient condition the minimum YS and UTS of Ni36 are 240 MPa and 450 MParespectively with representative test results showing the YS increasingfrom 270 MPa at room temperature to 700 MPa at LN₂ temperature. The EFis 40% over this temperature range. The thermal conductivities for Ni36at room temperature and LN₂ temperature are 6 & 13 W/m.° K respectively.

It can be seen that the properties of Ni36 are similar to that of 304for cryogenic service but with one notable exception. The average CTEover the temperature range from ambient conditions to LN₂ temperaturesis 1-2×10⁻⁶° K⁻¹ i.e. a length contraction of about 0.4 mm/m for thistemperature difference of 216° K. This is an order of magnitude lessradial contraction compared with austenitic stainless steel, which is aconsiderable advantage in improving the reliability of the sealingmechanism.

The corrosion resistance of a Ni36 for marine service may be achievedwith the deposition of a corrosion resistant cladding of anickel-chromium or nickel-copper alloy such as Inconel (trademark) orMonel (trademark) as examples.

In large bore hoses, e.g. 20″ to 24″ (500 to 600 mm), it is notpractical to control the thermal transients because of the volume ofcryogenic fluid that is involved. Furthermore, with increasing bore sizeand maintaining the high pressure retaining capacity results inincreasingly heavy end fittings which become difficult to handle anddeploy. We have found that there is a practical problem of achieving ahigh pressure capacity, light weight end fitting and to limit thethermal shock using the established metal based solution.

SUMMARY OF THE INVENTION

We have found that in order to solve the aforementioned end fittingissues for large bore hoses, it is possible to construct the end fittingcomponents from a composite material. It should be noted that thisreference to “composite material” differs from the use of the word“composite” in “composite hoses”.

Thus, according to one aspect of the invention we provide an end fittingfor a composite hose of the type comprising a tubular body of flexiblematerial arranged between inner and outer gripping members, said endfitting comprising a first member adapted to be disposed within thehose, and a second member adapted to be disposed around the outside ofthe hose, whereby the end of the hose can be sealed between the firstand second members, and wherein at least part of the first member and/orat least part of the second member is made of a composite material.

NOTATION AND NOMENCLATURE

The term “first member” represents the tail in the above discussion ofthe prior art, while the term “second member” represents the ferrule.

The first member may be made entirely of a composite material. However,we prefer that just the part of the material that is adapted to fitwithin the hose that is made of a composite material which expands oncooling.

“Composite materials” are materials that are made from a combination oftwo or more materials to give a unique and tailor made set ofproperties. The most common form of composite material is a matrix offibres within a resin. The fibres may be continuous with an orientationin the longitudinal direction or the fibres may be short lengths inmixed orientation. The fibres are usually high strength fibres such asE-Glass, S-Glass, Aramid (e.g. Kevlar (trademark)) or Carbon. The resinencapsulates the fibres and it may be a thermoplastic resin such as apolyethylene, a polyimide, a polyamide, a fluoropolymer,poly(vinylchloride) (PVC), polyurethane (PU), Polyetheretherketone(PEEK) or a thermosetting resin such as an epoxy or a polyester or avinyl ester. The composite material may be a laminated construction withlayers of longitudinal fibres in a resin matrix orientated in differingdirections in order to achieve the desired mechanical properties. Theuse of high strength fibres within the composite material generallyresults in a construction with a considerable strength to weight ratioand for this reason composite materials have found widespreadapplication in the aerospace and automotive industries includingpressure vessel applications.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompanying drawings in which:

FIG. 1 is a perspective view of a hose with which the end fittingaccording to the invention may be used.

FIG. 2 is a schematic cross sectional view of a first embodiment of anend fitting for a hose, according to the invention.

FIG. 3 is a schematic cross sectional view of a second embodiment of anend fitting for a hose, according to the invention.

FIG. 4 is a schematic cross sectional view of a third embodiment of anend fitting for a hose, according to the invention.

FIG. 5 is enlarged schematic cross sectional view of part of a hoseengaging member of the end fitting according to the invention beforeassembly.

FIG. 6 is enlarged schematic cross sectional view of part of a hoseengaging member of the end fitting according to the invention afterassembly.

DETAILED DESCRIPTION

Many of the constituent components of a composite material such as epoxyresin would not be suitable for cryogenic service in a bulk homogeneousform, mainly because of their brittleness at low temperatures. Howeverwhen the constituent materials are carefully combined in fibre andlaminate form with other constituent materials in a matrix then thestructural interaction is such that the constraints of the bulkhomogeneous constituent material may be overcome.

We have found that fibre selection is important and we prefer to use ahigh strength carbon, aramid, glass or ultra high molecular weightpolyethylene fibres or combinations thereof. For example, representativetensile strengths, tensile moduli and densities for E-Glass, Kevlar-49,MS-LM (Medium Strength Low Modulus) Carbon fibres are in order: 3450,3790, 4138 MPa for the tensile strength; 72, 124, 228 GPa for thetensile modulus; and 2.6, 1.4, 1.8 g/cc for the density. We have foundthat both thermosetting and thermoplastic resins may be used. Thedensity of epoxy and PEEK (polyetheretherketone) are both about 1.3g/cc. We have found that by using a composite material containing someof these high strength fibres, particularly in the first member,substantially reduces the weight of the end fitting while retaining thehigh pressure retaining capacity.

Another advantage of using a composite material is that it has a lowerthermal conductivity compared to steel. Typically the thermalconductivity is about 0.1 to 1 W/m.° K which is at least an order ofmagnitude less than austenitic stainless steel. This is particularlyadvantageous in cryogenic applications as it reduces the amount ofthermal insulation required for the end fitting to minimise the heatinflux causing boil of the cryogenic fluid. Gaseous boil off isinefficient in cryogenic liquid transfer and therefore it is highlydesirable to minimise the boil off rate. This is particularly importantin ship to ship transfer where the end fittings of a floating cryogenicflexible hose are in contact with water.

Because of the inherently lower thermal conductivity of composites it ispossible to build in successive layers of insulating materials orcomposites outside the internal composite layer by making use of theinherent thermal gradient. The insulating layers may be for examplehollow insulating fibres in a thermoplastic resin, or aeratedpolyurethane (PU). The use of PU gives a potentially robust outermechanical protective layer. Thus, the end first and/or second membersof the end fitting may be constructed of a plurality of layers ofmaterial, some or all of which are composite material, preferably havinga thermal conductivity of 2 W/m.° K or less, more preferably of 1 W/m.°K or less. Some layers of the first and/or second layer may be may ofnon composite materials, such as non-composite polymeric materialspreferably having a thermal conductivity below to 2 W/m.° K, morepreferably below to 1 W/m.° K. The non-composite materials may be athermoplastic resin or PU. Thus it is possible in accordance with theinvention to build the components of the end fitting out of layers ofmaterial designed to provided the desired bulk properties for the endfitting.

We have found that it is particularly advantageous to use the ratherunusual properties of carbon and certain aramid fibres, particularly thepoly-(p-phenyleneterephthalamide), known as Kevlar (trademark) or Twaron(trademark), in that they exhibit a negative longitudinal CTE and apositive transverse CTE. For example the longitudinal CTE for Kevlar-49is −2×10⁻⁶° K⁻¹ and in the transverse direction is 68×10-6° K⁻¹. In alaminated composite construction containing these fibres the ply expandsin the fibre direction and contracts transversely with reducingtemperature. We note that internal shear forces develop within abalanced symmetrical arrangement of plies and the result is a netlongitudinal expansion on cooling. By adjusting the fibre direction itis possible to control the magnitude the expansion to the point where aneffective longitudinal CTE from zero to about −10×10⁻⁶° K⁻¹ can beachieved. We are able to construct the composite tail to control themagnitude of the radial dimensional changes under the seal ring to eveneffect increasing sealing contact pressures with reduction intemperature. The preferred longitudinal CTE range is from below zero(e.g. below or equal to about −0.01° K⁻¹ or about −0.1° K⁻¹) to −4×10⁻⁶°K⁻¹, most preferably −1×10⁻⁶ to −2×10⁻⁶ ° K⁻¹.

Thus, in a preferred embodiment, at least part of the first memberand/or the second member is made of a material which expands in at leastone direction on cooling. It is particularly preferred that at leastpart of the first member expands on cooling—most preferably it is thepart of the first member that is adapted to be disposed within the hosewhich expands on cooling. Preferably the direction of expansion isradially outward of the first member, whereby the first member can exerta radially outward pressure on the inside of the hose when cooled.

In a particularly preferred embodiment, the first member is made atleast partially of a composite material which expands upon cooling, andthe second member is made at least partially of a composite materialwhich contracts upon cooling. As discussed above the expansion and/orcontraction is preferably in the direction which extends radially of thehose axis. In this embodiment, it is preferred that the first memberdoes not include composite material which contracts upon cooling, andthe second member does not include composite material which expands uponcooling.

According to another aspect of the invention there is provided an endfitting for a composite hose of the type comprising a tubular body offlexible material arranged between inner and outer gripping members,said end fitting comprising a first member adapted to be disposed withinthe hose, and a second member adapted to be disposed around the outsideof the hose, whereby the end of the hose can be sealed between the firstand second members, and wherein at least part of the end first memberand/or at least part of the first member is made of a material thatexpands in at least one direction upon cooling thereof.

We prefer that at least part of the first member, more preferably all ofthe first member, is made of a material that expands upon cooling.

The end fitting according to the above aspects of the inventiondescribed above may also be provided with one or more of the features ofthe end fitting already described in WO04/079248. These will bedescribed in greater detail below.

In a preferred embodiment, the second member includes a hose engagingmember adapted to press against the inner member to retain the hosebetween itself and the first member, and a separate means for retainingone or more layers of the hose, the retaining means comprising an outerretaining member adapted to press against an inner retaining member toretain the or each layer of the hose between the outer and innerretaining members of the retaining means.

Preferably, the inner and outer retaining members are ring-shaped. Morepreferably the inner and outer retaining members are preferably providedin the form of a ring, preferably with the outer retaining member beingdisposed concentric with the inner retaining member. More preferably,the first and second members are split rings, to facilitate assembly.

In a preferred embodiment, the outer retaining member which comes intocontact with the or each layer of the hose is provided with grippingformations to facilitate gripping of the or each layer of the hose. Thesurface of the inner retaining member may be provided with correspondingformations.

In a preferred embodiment, the adjacent surfaces of the inner and outerretaining members are provided with gripping formation to facilitategripping of the or each layer of the hose therebetween.

There may be any convenient number of inner and outer retaining members.In the simplest embodiment, there is one outer retaining member and oneinner retaining member. It is possible to provide two or more outerretaining members with one inner retaining member. It is possible toprovide two or more inner retaining members with one outer retainingmember. And it is possible to provide two or more outer retainingmembers with two or more inner retaining members, preferably so thateach outer retaining member has a corresponding inner retaining member.

The hose engaging member is preferably ring-shaped. The hose engagingmember is preferably in the form of a ring, more preferably a splitring. The hose engaging member preferably clamps all the layers of thehose securely between itself and the inner member of the end fitting.

In a preferred embodiment, the inner retaining member of the retainingmeans is integral with the hose engaging means. In this embodiment thehose engaging means comprises a first part of a first cross-sectionalthickness (i.e. diameter, when ring-shaped), and the integral innerretaining member comprises a second part of a second cross-sectionalthickness (i.e. diameter, when ring-shaped), the second thickness beingless than the first thickness. The outer retaining member may have athird cross-sectional thickness (i.e. diameter, when ring-shaped), andthe second and third cross-sectional thicknesses may be equal.Preferably, the sum of the second and third cross-sectional thicknessesis substantially the same as the first cross-sectional thickness.

When the inner retaining member is integral with the hose engagingmember, it is preferable that the hose engaging member is L-shaped, sothat the inner retaining member extends from the body of the hoseengaging member, and the outer retaining member can be receiving in therecess of the L-shape.

When the inner retaining member is integral with the hose engagingmember, the inner surface of the inner retaining member may alsofunction to clamp the hose fixedly between the hose between itself andthe inner member, i.e., it may contribute to the hose engaging function.

The hose engaging member and/or the retaining members may be made of acomposite material, as described above.

The first member may include an elongate tubular bend stiffener adaptedto fit within the hose body. The bend stiffener is preferably apolymeric material, most preferably polyurethane. Preferably the bendstiffener is tapered, such that the thickness decreases in a directionaway from the end of the hose; the degree of the taper may be optimisedfor each particular application. Preferably the tip of the bendstiffener (i.e. the part furthest from the end of the hose) is providedwith a shoulder against which any outer mechanical protection on thehose may be run.

In a preferred embodiment, the second member may further include a loadtransmitting member, and an end member, the arrangement being such thatthe hose engaging member and the end member are connected through theload transmitting member, whereby loads applied to the hose engagingmember can be transferred to the end member via the load transferringmember. In a preferred embodiment, the load transmitting membercomprises a cylindrical member has a first recess for receiving a partof the hose engaging member and a second recess for receiving part ofthe end member. The load transferring member may be made of a compositematerial, as described above. The end member may be made of a compositematerial as described above.

The end member of the second member is preferably integral with thefirst member.

According to another aspect of the invention, there is provided a hosecomprising a tubular body of flexible material arranged between innerand outer gripping members, and an end fitting as described abovesecured to each end of the hose.

The hose preferably comprises a tubular body and an axial reinforcingbraid disposed between inner and outer gripping members, wherein thetubular body comprises a reinforcing layer and a sealing layer.Preferably there are inner and outer reinforcing layers, and the sealinglayer is sandwiched between the reinforcing layers.

The hose preferably further comprises a protective and/or insulativelayer wrapped around said hose, wherein said protective and/orinsulative layer has an end portion which is adapted to be received inthe first recess of the cylindrical load transferred member.

Although more than one layer of the hose may be retained by theretaining means of the end fitting, it is particular preferred that thebraid alone of the hose is retained between the inner and outerretaining members of the retaining means.

As mentioned above the hose and end fitting can be provide with anycombination of the features of the hose and end fitting described inWO01/96772, WO04/044472 and WO04/079248 the contents of which areincorporated by reference.

The hose according to the invention can be provided for use in a widevariety of conditions, such as temperatures above 100° C., temperaturesfrom 0° C. to 100° C. and temperatures below 0° C. With a suitablechoice of material, the hose can be used at temperatures below −20° C.,below −50° C. or even below −100° C. For example, for LNG transport, thehose may have to operate at temperatures down to −170° C., or evenlower. Furthermore, it is also contemplated that the hose may be used totransport liquid oxygen (bp −183° C.) or liquid nitrogen (bp −196° C.),in which case the hose may need to operate at temperatures of −200° C.or lower.

The hose according to the invention can also be provided for use at avariety of different duties. Typically, the inner diameter of the hosewould range from about 2 inches (51 mm) to about 24 inches (610 mm),more typically from about 4, 6 or 8 inches (203 mm) to about 16 inches(406 mm). In general, the operating pressure of the hose would be in therange from about 500 kPa gauge up to about 2000 kPa gauge, or even up toabout 4000 kPa gauge, or higher. These pressures relate to the operatingpressure of the hose, not the burst pressure (which must be severaltimes greater). The volumetric flow rate depends upon the fluid medium,the pressure and the inner diameter. Flowrates from 1000 m³/h up to12000 m³/h are typical.

The hose according to the invention can also be provided for use withcorrosive fluids, such as strong acids.

The type of hose to which this invention applies is described in detailin WO01/96772. FIG. 1 shows the hose 100 in more detail.

Briefly, the hose 100 comprises inner and outer gripping members 102 and104, which are preferably arranged in a helical form, and are preferablywires. A tubular body 106 and an axial reinforcing braid 108, whichsurrounds the tubular body 106, are arranged between the grippingmembers 102 and 104. The tubular body comprises an inner reinforcinglayer 110, and outer reinforcing layer 112 and a sealing layer 114arranged between the inner and outer reinforcing layers 110 and 112. Anouter protective/insulative layer 116 surrounds the braid 108. Asmentioned above the hose 100 is described in greater detail inWO01/96772, the contents of which are incorporated herein by reference.

The ends of the hose may be sealed using the end fitting 200 shown inthe figure. The hose has not been shown in the figure, in order toimprove the clarity. The end fitting 200 comprises a tubular innermember 202 having a hose end 202 a and a tail end 202 b. The part 202 ais advantageously a composite material which expands in at least onedirection on cooling, most preferably in the direction radial to thehose 100 longitudinal axis. The tail end may also be made of a compositematerial, to reduce the weight of the assembly. The end fitting 200further includes a sealing member which comprises a sealing ring 204,which is typically based on a polymeric resin such as PTFE, optionallywith a ceramic filler, and a stainless steel split ring 206 around thesealing ring 204. The ring 206 may be made of a composte material.

The end fitting 200 further includes a load transferring means whichcomprises a hose engaging member 208, a load transferring member 210 andan end member in the form of a disk-shaped plate 212. The plate 212 isintegral with the tail end 202 b of the inner member 202, as illustratedat 212 b. The load transferring member comprises a disk-shaped plate 214and at least one load transferring rod 216. In the figure there are twoof the rods 216, but it is preferable to provide three or more of therods 216, and it is preferable that the rods are equi-spaced around thecircumference. A tightening nut 218 is provided on each rod 216. Theplates 212 and 214 have apertures 212 a and 214 a respectively forreceiving the rods 216. One or more, or all, of the parts 210, 212, 214,216 and 218 may be made of a composite material which expands in atleast one direction on cooling.

The hose engaging member 208 is provided with an inner helical recess inthe form of grooves 208 a which are adapted to receive the outer wire ofthe hose therein. The inner member 202 is provided with an outer helicalrecess in the form of grooves 202 d which are adapted to receive theinner wire 22 therein. The grooves 208 a and 202 d are spaced by half apitch length p, where p is the pitch length of the gripping wires of thehose (not shown).

The hose engaging member 208 also includes a retaining means forretaining the braid 108 of the hose 100. The retaining means comprisesan inner retaining member 230 which is integral with the rest of thehose engaging member, and a separate outer retaining member 232. Theouter 232 is capable of clamping the braid 108 of the hose 100 betweenitself and the inner member 230. The outer member 232 has grippingformations on the inner surface thereof to facilitate gripping the braid108 between the outer member 232 and the inner member 230. The grippingformations are preferably circumferential but can take other patterns.

The parts 206, 208, 230 and 232 are preferred to contract on cooling.This can be achieved by making them of steel or a composite materialwhich contracts in at least one direction on cooling.

The member 202 is provided with two circumferential projections 202 ewhich are located under the sealing ring 204. The projections 202 eserve the improve the sealing of the tubular member between the innermember 202 and the sealing ring 204, and help to prevent the tubularmember from inadvertently being pulled out of position.

The end fitting 200 is also provided with a flexible polymeric bendstiffener 240 which has apertures 242 through which the rods 216 may bereceived. One end of the bend stiffener 240 abuts the plate 214. Theparts 202 e and 240 may be made of a composite material which expands inat least one direction on cooling. FIG. 3 shows an end fitting which issimilar to the end fitting shown in FIG. 2, and the same referencenumerals have been used to designate the parts. The differences are: thebend stiffener is not provided in the design shown in FIG. 2, althoughit could be, if desired; the plates 212 and 214 have a smaller diameter,so that the structure is more compact.

FIG. 4 shows an end fitting which is similar to the end fitting shown inFIG. 2, and the same reference numerals have been used to designate theparts. In FIG. 4 the load transferring rod has been replaced by a loadtransferring member 250 which has recesses 250 a and 250 b adapted toreceive the edges of plates 212 and 214 respectively. The part 250 maybe made of a composite material which expands in at least one directionon cooling.

The recess 250 b also receives and end portion 260 a of a protectiveand/or insulative layer 260 provided on the outer surface of the hose100 (i.e. provided outside the gripping member 104. The layer 260 may bethe same sort of layer as described in our copending internationalpatent publication WO04/044472. This comprises an elongate profiledmember which is wrapped helically around the outside of the hose 100.

Reference is now made to FIGS. 5 & 6. For the axial reinforcing braid108 to function most effectively, it should be securely anchored at theend fitting 200. The outer member 232 mates with the inner member 230 toprovide this anchor. This interface is designed to reduce to zero thetension in the braid 108, caused by hose pressure and tension, in orderto help prevent the braid 108 from being pulled from the anchor.

When the braid 108 is pulled axially it tries to reduce its radius,owing to the braid structure. If it is prevented from reducing itsradius then a contact pressure is generated equal to the local tensiontimes the local curvature. To illustrate the concept of local curvature,consider a string were wrapped around a cylinder, where the localcurvature is the reciprocal of the cylinder radius. This contact forcetimes the local friction coefficient anchors the braid 108 (this is theso called “capstan” effect). The frictional force is non-linear becauseof the undulating formations 230 a and 232 a on the members 230 and232—it would be linear if it were straight plates. Non-linear decay ismore effective.

The braid folds back out of the hose body around a filleted front edge230 b of the member 230. The filleted edge 230 b prevents large stressconcentrations being induced in the braid 108 as a result of the contactof the braid 108 with the member 232 under tension. This radius controlsthe contact pressure generated by the tension in the braid 108. The dropin tension is a non-linear function of the product of the angle ofcontact the braid makes with the radius and the local frictioncoefficient. In the case shown, where the radius of the fillet isconstant, the non-linear function is exponential.

When the outer member 232 is fully mated against the inner member 232the profiled surfaces 230 a and 232 a of the first and second membersrespectively mate closely thus forcing the braid 108 to pass through aseries of undulations. Each undulation acts as a capstan and so reducesthe tension in the braid as described earlier.

The hose is secured to the end fitting 200 as follows. The inner member202 is threaded into the end of the hose, so that the hose lies close tothe plate 212. The inner wire of the hose is received in the grooves 202d and the outer wire of the hose is received in the grooves 208 a. Theinner and outer wires are cut back so that they do not extend along theinner member 202 beyond the grooves 202 d and 208 a. Any insulation ofthe hose is also cut back to this point. The inner reinforcing layer ofthe hose is also cut back at this point, or at some point before itreaches the sealing ring 204. This means that the sealing layer of thehose directly engages the outer surface of the inner member 202. Therest of the tubular body of the hose is allowed to extend along theinner member 202 between the inner member 202 and the sealing ring 204.

The hose engaging member 208 is then tightened to cause it to clamp downon the hose bring it into firm engagement with the hose. The nuts 218are then tightened, which induces some axial tension in the hose,thereby taking up any play in the system. These forces are transmittedfrom the hose engaging member 208, to the plate 214, to the rod 216, tothe plate 212, and to the tail end 202 b of the inner member 202. Thetubular member is pulled back over the upper surface of the hoseengaging member 208, and between the outer member 232 and the innermember 230. The second outer 232 and the inner member 230 clamp thebraid 108 firmly in place.

The tubular body 106 of the hose 100 extends under the sealing ring 204.After the hose engaging member 208 and the nuts 218 have been tightened,the split ring 206 is tightened in order to increase the force appliedon the tubular body by the sealing ring 204.

The end fitting 200 is then cooled to a low temperature by liquidnitrogen. This causes the sealing ring 204 to contract relatively morethan the split ring 206, whereby the compressive force applied on thesealing ring 204 by the split ring 206 is reduced. While the split ring206 and the sealing ring 204 are at a relatively low temperature, thesplit ring 206 is again tightened. The temperature is then allowed torise to ambient conditions, whereby the compressive force on the sealingring increases by virtue of the greater expansion of sealing ring 204relative to the split ring 206.

It will be appreciated that the invention described above may bemodified. For example, the inner retaining member 230 could be separatefrom the rest of the hose engaging member. Furthermore, additional innerand outer retaining members 230 and 232 may be provided.

1. An end fitting for a composite hose of the type comprising a tubular body of flexible material arranged between inner and outer gripping members, said end fitting comprising a first member adapted to be disposed within the hose, and a second member adapted to be disposed around the outside of the hose, whereby the end of the hose can be sealed between the first and second members, and wherein at least part of the first member and/or at least part of the second member is made of a composite material.
 2. The end fitting according to claim 1, wherein at least part of the first member is made of a composite material.
 3. The end fitting according to claim 1, wherein the composite material comprises carbon, aramid, glass or UHMWPE fibres.
 4. The hose according to claim 1, wherein at least part of the second member is adapted to contract on cooling in a direction radial inward with respect to the hose axis.
 5. The hose according to claim 1, wherein at least the part of the first member which is disposed, in use, within the hose, is made of a composite material which is adapted to expand in at least one direction on cooling.
 6. The hose according to claim 5, wherein said part of the first member is adapted to expand on cooling in a direction radial outward with respect to the hose axis.
 7. The end fitting according to claim 5, wherein longitudinal coefficient of thermal expansion of the composite material which expands upon cooling is from zero to −10×10⁻⁶° K⁻¹.
 8. The end fitting according to claim 5, wherein the composite material which expands upon cooling comprises carbon fibres or fibres of poly-(p-phenyleneterephthalamide).
 9. The end fitting according to claim 5, wherein the first member is made at least partially of a composite material which expands upon cooling, and the second member is made at least partially of a composite material which contracts upon cooling.
 10. An end fitting for a composite hose of the type comprising a tubular body of flexible material arranged between inner and outer gripping members, said end fitting comprising a first member adapted to be disposed within the hose, and a second member adapted to be disposed around the outside of the hose, whereby the end of the hose can be sealed between the first and second members, and wherein at least part of the end first member and/or at least part of the first member is made of a material that expands upon cooling in at least one direction thereof
 11. The end fitting according to claim 10, wherein at least part of the first member is made of a material that expands upon cooling in at least one direction thereof.
 12. The end fitting according to claim 10, wherein longitudinal coefficient of thermal expansion of the material which expands upon cooling is from zero to −10×10 ⁻⁶° K⁻¹.
 13. The end fitting according to claim 10, wherein the material which expands upon cooling is a composite material comprising carbon fibres or fibres of poly-(p-phenyleneterephthalamide).
 14. The end fitting according to claim 10, wherein the first member is made at least partially of composite material which expands upon cooling, and the second member is made at least partially of a composite material which contracts upon cooling.
 15. A hose comprising a tubular body of flexible material arranged between inner and outer gripping members, a further comprising an end fitting according to claim 1 secured to each end of the hose.
 16. The hose according to claim 15, wherein the tubular body comprises a reinforcing layer and a sealing layer.
 17. The hose according to claim 15, wherein the tubular body comprises inner and outer reinforcing layers and a sealing layer disposed between the inner and outer reinforcing layers.
 18. The hose according to claim 15, further comprising an axial strengthening means.
 19. The hose according to claim 18, wherein the axial strengthening means comprises an axial reinforcing braid.
 20. (canceled) 